Currently, research on an automatic driving technique of an automobile has been actively conducted in each country, and each country is considering the legislation so as to enable a vehicle (hereinafter, a “vehicle” refer to an automobile) to travel in an automatic driving mode on public roads. Here, in the automatic driving mode, a vehicle system automatically controls travelling of a vehicle. Specifically, in the automatic driving mode, the vehicle system performs at least one of a steering control (control a travelling direction of the vehicle), a brake control and an accelerator control (control of braking and acceleration/deceleration of the vehicle) based on various information obtained from a camera, a sensor, a radar and the like. On the other hand, in a manual driving mode to be described later, a driver controls the travelling of the vehicle, as in most of conventional vehicles. Specifically, in the manual driving mode, the travelling of the vehicle is controlled in conformity with a driver's operation (a steering operation, a braking operation, and an accelerator operation), and the vehicle system does not automatically perform the steering control, the brake control and the accelerator control. Meanwhile, the driving mode of the vehicle is not a concept existing only in some vehicles but a concept existing in all vehicles including conventional vehicles having no automatic driving function. For example, the driving mode of the vehicle is classified in accordance with a vehicle control method or the like.
Thus, in the future, it is expected that vehicles travelling in the automatic driving mode (hereinafter, appropriately referred to as “automatic driving vehicle”) and vehicles travelling in the manual driving mode (hereinafter, appropriately referred to as “manual driving vehicle”) coexist on public roads. Particularly, in a situation where the vehicles travelling in the automatic driving mode and the vehicles travelling in the manual driving mode coexist, it is preferable that a state of inter-vehicle communication between one automatic driving vehicle and the other automatic driving vehicle is presented to an outside, from a standpoint of safety.
Patent Document 1 discloses an automatic follow-up travelling system in which a following vehicle can automatically follow a preceding vehicle. In the automatic follow-up travelling system, each of the preceding vehicle and the following vehicle has a display device, character information for preventing the other vehicle from intruding between the preceding vehicle and the following vehicle is displayed on the display device of the preceding vehicle, and character information indicative of the automatic follow-up travelling mode is displayed on the display device of the following vehicle.